It is known to determine a geographic position by measuring angles to stars or satellites, such as by a star camera. It is also known to navigate by matching images of stars or terrain to known images at predetermined locations, such as along a trajectory. In addition, visual odometry has been used to determine position and/or orientation of robots and vehicles. However, these methods suffer from various limitations.
For example, celestial sightings require clear sky. Clouds obscure the sky, and sky glow reduces contrast, thereby making it difficult or impossible to determine a position or navigate using celestial sightings. Furthermore, celestial sightings-based navigation is not extremely accurate.
Direct landmark imaging requires a matchable landmark to be available and visible. Typically, landmark matching systems use downward-looking cameras to image terrain. However, such landmarks are often unavailable or not visible, particularly at ground level, such as from the point of view of a dismounted hiker.
Visual odometry is a relative navigation technique characterized by error that increases as a function of distance traveled.
Improved position determination and navigation techniques would be beneficial.